Acids & Bases: Red Cabbage pH Paper

You can probably tell that some foods are acidic because of how they taste (oranges, for example). In this science project, we'll use the juice from a colorful vegetable to indicate the pH level of different liquids and find out just how acidic or basic they are!
Learn how to use red cabbage to find out if a liquid is an acid or base.

Part 1: Make pH Test Strips

This part of the project requires chopping and cooking. Make sure you have an adult to help before you begin!

What You Need:

• half a red cabbage 
• saucepan 
• colander/strainer 
• bowl 
• rimmed baking sheet 
• paper towels 
• filter paper or coffee filter

What You Do:

1. Ask an adult to chop the cabbage into small pieces. Put the pieces in the saucepan and cover with water.
   
   
2. With an adult’s help, heat the pan on the stove until the water begins to boil, then turn the heat to low and let the cabbage simmer for 20 minutes. Stir occasionally.
   
   
3. Let the cooked cabbage cool slightly, then have an adult pour the contents of the pot through the strainer, collecting the purplish cabbage liquid in a bowl.
4. Discard the cooked cabbage. Make sure to clean up any drips as you go because the cabbage liquid can stain.
5. Once the liquid is cool enough to touch, place the paper rectangles into the bowl and stir them around for a moment, then allow them to soak for about five minutes or until they have turned blue or purple.
   
   
6. Remove each paper and place it on a cooling rack to dry (put a rimmed baking sheet lined with paper towels under the rack to catch drips). Let the papers dry completely.
   
   
7. Once dry, cut the rectangles into strips about 1/2" wide. Use these test strips for Part 2 of the experiment.
   
   

Part 2: Test Liquids for pH

Now for the exciting part of the project—see how different substances change the color of the test strips depending on how acidic or alkaline (basic) they are!

What You Need:

• test tubes and stand (or small jars) 
• liquids from around your house to test (see list below) 
• red cabbage test strips from above 
• liquid substances to test* 
• worksheet to track results 

What You Do:

1. Pour a small amount of each liquid into a separate test tube.
   
   
2. Dip one test strip into each test tube and place it on a paper towel next to that tube. (Use a wooden skewer to pull the strip out if it isn’t long enough to grab with your fingers.)
   
   
3. Watch the test strips and note any changes in color on the paper.
   
   
4. Keep track of your results with this worksheet. You can even tape the test strips into the spaces once they’re dry. Note that the colors will lighten as they dry, so make sure to write down your results before the strips dry!

*Substances to Test (choose at least 6):

• Lemon juice 
• Apple juice 
• Cola or another soda 
• Coffee or tea 
• Milk 
• Vinegar 
• Baking soda (mix 1 teaspoon with 1 tablespoon of water) 
• Dish soap or laundry detergent (mix 1 teaspoon with 1 tablespoon of water) 
• Eggs (whisk the yolks and whites together) 
• Antacid, such as Tums (crush a tablet with the back of a spoon and dissolve in 1 tablespoon of water)

What Happened:

The pigment that gives red cabbage its color is called anthocyanin. It is also the pigment found in leaves that turn red or purple in the fall. Anthocyanin is a good indicator of acids and bases, as you saw from the changing colors in this experiment. When added to a base, the purplish pigment turns green or yellow and when added to an acid, it changes to pink or red. In something that is neutral (neither an acid nor a base), the paper will remain the same color (or maybe turn a little blue).

Source: Red Cabbage pH Paper

Big Dry Ice Bubble

Have fun making a dry ice bubble that will grow and grow as it fills with fog. This experiment is a great one for adults to do with kids. Add water to the dry ice, cover it with a layer of soapy water and watch your bubble grow, how big will it get before it bursts? Give it a try and find out!

What you need:

• Water
• A large bowl with a lip around the top (a smaller bowl or cup will work too)
• A strip of material or cloth
• Soapy mixture for making bubbles (water and some dishwashing liquid should do the trick)
• Dry ice - one piece for a cup, more for a bowl. Places where adults can buy dry ice include large grocery stores. Butchers and ice cream stores might have some too.

Safety first! Be careful with dry ice as it can cause skin damage if not used safely. Adults should handle dry ice with gloves and avoid directly breathing in the vapor.

Instructions:

1. Place your dry ice in the bowl and add some water (it should start looking like a spooky cauldron).
2. Soak the material in your soapy mixture and run it around the lip of the bowl before dragging it across the top of the bowl to form a bubble layer over the dry ice.
3. Stand back and watch your bubble grow!

What's happening?

Dry ice is carbon dioxide (CO₂) in its solid form. At temperatures above -56.4 °C (-69.5 °F), dry ice changes directly from a solid to a gas, without ever being a liquid. This process is called sublimation. When dry ice is put in water it accelerates the sublimation process, creating clouds of fog that fill up your dry ice bubble until the pressure becomes too much and the bubble explodes, spilling fog over the edge of the bowl. Dry ice is sometimes used as part of theater productions and performances to create a dense foggy effect. It is also used to preserve food, freeze lab samples and even to make ice cream!

Source: Dry Ice Bubble

Make an Easy Lava Lamp

Learn how to make an easy lava lamp with this fun science experiment. Use simple household items such as vegetable oil, food coloring, Alka-Seltzer and a bottle to create chemical reactions and funky balls of color that move around like a real lava lamp.

What you need:

• Water
• A clear plastic bottle
• Vegetable oil
• Food coloring
• Alka-Seltzer (or other tablets that fizz)

Instructions:

1. Pour water into the plastic bottle until it is around one quarter full (you might want to use a funnel when filling the bottle so you don't spill anything).
2. Pour in vegetable oil until the bottle is nearly full.
3. Wait until the oil and water have separated.
4. Add around a dozen drops of food coloring to the bottle (choose any color you like).
5. Watch as the food coloring falls through the oil and mixes with the water.
6. Cut an Alka-Seltzer tablet into smaller pieces (around 5 or 6) and drop one of them into the bottle, things should start getting a little crazy, just like a real lava lamp!
7. When the bubbling stops, add another piece of Alka-Seltzer and enjoy the show!

What's happening?

If you've tried our oil and water experiment you'll know that the two don't mix very well. The oil and water you added to the bottle separate from each other, with oil on top because it has a lower density than water. The food coloring falls through the oil and mixes with the water at the bottom. The piece of Alka-Seltzer tablet you drop in after releases small bubbles of carbon dioxide gas that rise to the top and take some of the colored water along for the ride. The gas escapes when it reaches the top and the colored water falls back down. The reason Alka-Seltzer fizzes in such a way is because it contains citric acid and baking soda (sodium bicarbonate), the two react with water to form sodium citrate and carbon dioxide gas (those are the bubbles that carry the colored water to the top of the bottle).

Adding more Alka-Seltzer to the bottle keeps the reaction going so you can enjoy your funky lava lamp for longer. If you want to show someone later you can simply screw on a bottle cap and add more Alka-Seltzer when you need to. When you've finished all your Alka-Seltzer, you can take the experiment a step further by tightly screwing on a bottle cap and tipping the bottle back and forth, what happens then?

Source: Lava Lamp

Build a Pinhole Camera

Today, nearly everyone has a digital camera, and it’s easy to take a perfect photograph every time. But like many electronics, cameras may seem mystical and complicated to your child, and they can be expensive too! This project teaches how simple a camera can be, and how light forms an image on the film. It’s an inexpensive project, a great science experience to learn about optics, and a fun art activity, too! Best of all, making the camera is only the beginning.

The pinhole camera was the first camera ever invented, and it’s very simple—made up of only a small aperture, a shutter, a light-proof container, and some film. The images produced are surreal, artsy, and quite unique. To start the activity, you may want to show your child the differences in quality and style between old photographs and today’s images. Your child will be amazed that she can build her own camera and take her own artistic photographs!

What You Need:

• 35mm film
• A small box: wood, metal, plastic, or cardboard. It should have room to hold film canisters on both sides and still allow space in the middle for taking the photograph (a 7 inch cube or larger works best)
• 1/4" wooden dowels
• Black marker
• Black spray paint
• Heavy cardboard
• Aluminum foil
• Sewing needle or sewing pin
• Craft glue
• Used sewing thread spool or wooden spools
• Electric drill
• Hacksaw or dremel cutting tool

Note: Because of the different steps and tools involved, make sure to work under the supervision of your teacher .

What You Do:

1. Start by setting up your film canister. Your film canister will sit on one side of the box, and the film will wind across the aperture into the other side. Measure where the head of your film canister sits, and drill another 1/4" hole there. This should allow space to fit the dowel into the hole, and into the top of the canister so you can wind film as you take photos.
2. You will need to build the spaces to hold your film canister, and used film, in place while you use the camera. Cut pieces of cardboard to separate these sections of the interior. Check to make sure they fit snugly and allow room for the film, and glue them in place.
3. Measure the size you’ll need for your dowel. It will need to fit into your spool, which will wind your film, then slot through the top hole into the camera and plug into your film canister. Once you know the right length, saw the dowel to the right size using a hacksaw or dremel. While you have the saw, you’ll also want to slot the end of the dowel so it fits snugly into the film canister for rotation.
4. Once you have your box and dowel ready, take them to a ventilated area and spray paint them black on the inside. This will help reduce the light and keep the film protected.
5. While your paint dries, work on making the aperture for your camera. Use tin foil, or a piece cut from an aluminum soda can. Take a sewing needle or pin, and carefully rotate it in order to drill a hole into the aluminum. Do this slowly, rather than punching right through the metal, because you’ll want it to be smooth.
6. Once you have a small hole, even it out by using sandpaper to sand off sharp . You may want to once more work the pin through and sand it once more to make sure the aperture is even and well-formed. Remember, this is how light comes into the camera and will help determine your image quality.
7. Now it’s time to make a shutter, the piece that attaches in front of your aperture so you can control when to take a picture. Cut out a small piece of cardboard that will fit the front of your camera on top of the hole you made. Color it black on the inside and cover it with black tape. , and attach this in front of the hole so that no light can sneak in.
8. Once your paint is dry, attach the shutter to the front of the camera’s drilled hole using black tape.
9. Next, attach the little pinhole aperture you made from the aluminum to the camera to the inside of the box. Use a small piece of masking tape or electrical tape, with a chunk cut out of the center, and center it over the larger hole you drilled for the aperture in the center.
10. Color the masking tape with a black marker to make it less reflective and more light-proof from the inside.
11. Next, mount your pieces together: attach the dowel and spool, and work them through the box, into your film canister. You may want to cut and use a small black felt washer on your dowel, between the wood spool and the camera, to prevent extra light from leaking in.
12. In order to wind the film without opening the camera, you will need to know how many turns to make on your spool. Make a mark on the spool, and on the top of the camera next to the spool, so you can measure how far you’re turning it.
13. Pull some of the film from your canister and wind it to the other side of your box. Using a black Sharpie, mark the space where your film will get exposed (from each piece of cardboard to the next). Then, wind the film back into the canister, paying attention to how many rotations are needed to move the film to the next exposure.
14. Check once or twice more to see an average of how far to wind the spool when you take a photo.
15. You will need to go into a dark place for the next step! Notice that you can’t pull film out of the spool by winding, only rewind film into the spool. So, you will need to unwind the film into the other side of the camera, then wind the film back into the canister, while you take pictures. However, if you wind film anywhere where there is light, the film will get exposed and you won’t be able to shoot with it. So, go into a dark room and unwind the film by feeling where it should go, into the opposite side of your camera. Then, close up your box carefully.
16. To make sure your box is light-proof, use black photo or electric tape to secure all the openings from your box while you take photographs.

Now, you’re ready! To take a picture, hold the camera very steady and point it toward what you want to photograph. Open the shutter carefully, so light can reach in your aperture. Use the following guidelines for exposure with ISO 100 or 200 film:

• Outdoors in bright sun: 2–3 seconds 4.
• Outdoors when overcast or shaded: 5 seconds 5.
• Indoors with normal room lighting: 5–10 minutes

If you want to attach the camera to a tripod, you can simply use a few rubber bands to hold it on.

When you’ve used your roll of film, you can take it to a drug store to develop it, just as you would with a normal film camera. You may want to let them know that you were using a pinhole camera and that your picture sizes may be abnormal, so they can take care when developing them. Hang your photos on the refrigerator, or along the walls in your home to show off your new creations!

Reference: Pinhole Camera

Lumpy Liquids and Squishy Solids

Have you ever turned a liquid into a solid just by tapping on it? In this experiment you make just such a liquid.

For this experiment you will need:

• corn starch (about ¼ cup, or 60 cm³)
• water (about ¼ cup, or 60 cm³)
• a bowl for mixing
• newspaper

Place a sheet of newspaper flat on a table. Put the mixing bowl in the middle of the newspaper. Add ¼ cup of dry cornstarch to the bowl. Add about 1/8 cup (2 tablespoons, or 30 cm³) of water to the corn starch and stir slowly. Add water slowly to the mixture, with stirring, until all of the powder is wet.

Continue to add water until the cornstarch acts like a liquid when you stir it slowly. When you tap on the liquid with your finger, it shouldn't splash, but rather will become hard. If your mixture is too liquid, add more cornstarch. Your goal is to create a mixture that feels like a stiff liquid when you stir it slowly, but feels like a solid when you tap on it with your finger or a spoon.

Scoop the cornstarch mixture into the palm of your hand, then slowly work it into a ball. As long as you keep pressure on it by rubbing it between your hands, it stays solid. Stop rubbing, and it “melts” into a puddle in your palm. Can you think of other tests you can do with it?

Why does the cornstarch mixture behave like this?

Think of a busy sidewalk. The easiest way to get through a crowd of people is to move slowly and find a path between people. If you just took a running start and headed straight for the crowd of people, you would quickly slam into someone and you wouldn't get very far. This is similar to what happens in the cornstarch mixture. The solid cornstarch acts like a crowd of people. Pressing your finger slowly into the mixture allows the cornstarch to move out of the way, but tapping the mixture quickly doesn't allow the solid cornstarch particles to slide past each other and out of the way of your finger.

We use the term “viscosity” to describe the resistance of a liquid to flow. Water, which has a low viscosity, flows easily. Honey, at room temperature, has a higher viscosity and flows more slowly than water. But if you warm honey up, its viscosity drops, and it flows more easily. Most fluids behave like water and honey, in that their viscosity depends only on temperature. We call such fluids “Newtonian,” since their behavior was first described by Isaac Newton (when he wasn’t discovering the laws of gravity or developing the calculus). The cornstarch mixture you made is called “non-Newtonian” since its viscosity also depends on the force applied to the liquid or how fast an object is moving through the liquid.

Other examples of non-Newtonian fluids include ketchup, silly putty, and quicksand. Quicksand is like the cornstarch mixture: if you struggle to escape quicksand, you apply pressure to it and it becomes hard, making it more difficult to escape. The recommended way to escape quicksand is to slowly move toward solid ground; you might also lie down on it, thus distributing your weight over a wider area and reducing the pressure. Ketchup is the opposite: its viscosity decreases under pressure. That’s why shaking a bottle of ketchup makes it easier to pour.

Disposal: First dilute the cornstarch mixture with plenty of water before pouring it down the drain. Why? What do think would happen to the semi-solid, semi-liquid form that you prepared if pressure were applied to it by other water in the drain? Yes – a plugged drain.

Try it and have fun!

Source: Non-Newtonian Fluid Experiment

Bottled Ballons: A Respiratory System Activity

Objectives:

• Explain how the lungs work.
• Describe how the movement of the diaphragm helps the air go in and out of the the lungs.

Materials:

   1 two-liter empty plastic bottle 

   3 balloons (1 big, 2 small)

   1 sturdy straw

   1 pair of scissors

   5 rubber bands

Procedure:

• Using a pair of scissors, cut the bottom out of the 2-liter plastic bottle.
• Create two holes that are apart from each other in the cap pf the plastic bottle. Make sure the each hole is just big enough for a straw to fit through.
• Stick the two straws through the two holes of the bottle cap.
• Place one balloon on the end of each straw, and secure them with rubber bands, as shown in the figure below.

• Stick the balloon on ends of the straws through the bottle opening and screw the lid on tightly.
• Stretch out the larger balloon and place it over the open bottom of the bottle. Secure it with the rubber band as tightly as possible. Refer to the diagram of the finished lung model below. 

• Pull the larger balloon down; that is, away from the bottle, in order to blow up the two small balloons.
• Push the larger balloon towards the bottle in order to let the air out of the two small balloons.

Try the activity and discover how the lungs work! Have fun and learn!

Source: Bottled Balloon Activity