This is a great lab to do at home, without having to go out and buy, well, probably anything! Chances are you can put out everything the kids need with just a few minutes of prep time. And, it’s a great supplement to any homeschool science curriculum. This lab uses soda bottle test tubes. These are AMAZING! Made of very durable plastic and with snug-fitting lids, they are much more user-friendly than small and fragile test tubes. This is a great homeschool science lab to do whenever the weather is icky, or you just want to let the kids explore.
Before you start this lab, remind kids of the lab safety rules
Kids should be wearing goggles, gloves and lab coats for this lab. Long hair should be tied up.
Soda bottle test tubes and rack
Different household chemicals (glass cleaner, dish soap, diluted or liquid laundry detergent, kitchen cleaner, and so on)
pH test strips
pH color chart
Prepare by prefilling each test tube with about 30 mL of each household chemical. Do NOT mix the chemicals. Carefully supervise the kids so that they don’t mix the chemicals. Keep one test tube for tap water (or distilled if you have it on hand). This is your CONTROL. Control is a term that means the sample that you’re going to compare against.
- ASK your kids what it is like to eat a lemon? What does it taste like? What do we call the taste of a lemon (sour).
- EXPLAIN to the kids that scientists realized that the sour taste of a lemon is related to certain types of chemicals called acids. Some common acids are citric acid and ascorbic acid. If they’ve ever had sour candies, they were probably coated with citric acid.
- REMIND the kids that scientists don’t use taste as a method for finding out if an acid is present, then ask them why. (Because eating chemicals is dangerous!)
- TELL the kids that scientists have also discovered that another kind of chemical, bases, have a bitter taste.
- DISCUSS: When scientists explored acids and bases, they came up with a scale that could describe how acidic or basic things are. The scale goes from 0-14, with 0 being the strongest acid and 14 being the strongest base.
- ASK the kids what 7 might represent? (neutral)
- ASK the kids what substance they drink every day is pretty close to neutral? (water). Explain that PURE WATER has no minerals or chemicals in it and is a 7 on the pH scale. However, tap and bottled water have dissolved minerals and chemicals in it that can slightly alter the acidity or basic properties of the water.
- DEMONSTRATE how to use a pH strip. The kids should hold the tip of the strip with tweezers, and tip the end of it into the first test tube of liquid. They then compare the color on the test strip to the color key on the inside of the pH paper packet.
If the kids have a science journal, you can have them (or you do it) draw a chart so that they can practice recording quantitative data. This is an important skill to develop early on, and one that is often neglected in traditional homeschool science curriculum. The names of each household chemical can go down the side, and the kids can record the (approximate) pH level next to it. They can practice making hypotheses by guessing which liquid is a base, neutral or acid. Record their hypotheses in another column in their data sheet.
REVIEW with the kids which chemicals were more or less acidic.
To clean up, rinse the chemicals down the sink with plenty of water. Wash out the test tubes and leave to dry. Discard used pH strips.